Compressor control for refrigeration system

ABSTRACT

A combination equalizer and over-pressure control for use with fluid compressors comprises a passage having a first piston including a relief port therethrough, the piston when in a first position preventing any flow of fluid through a second relief port. A second piston, disposed upstream of the first piston, is movable relative thereto. A first spring provides a force to maintain the second piston in spaced relationship relative to the first piston, the second piston moving into sealing abutment with the first piston to close the first relief port when fluid pressure acting on the second piston exceeds a predetermined value. A second spring provides a force to maintain the first and second pistons in position relative to the second relief port to prevent any fluid flow therethrough. The first and second pistons move jointly at a predetermined over-pressure condition to open the second relief port. Upon the deenergization of the fluid compressor the second piston moves relative to the first piston, whereby the first relief port is opened to relatively quickly equalize pressures across the control.

llnited States atent- 1191 St. Laurent 1451 Dec. 24, 1974 COMPRESSORCONTROL FOR REFRIGERATION SYSTEM [76] Inventor: Arthur St. Laurent, 240S Main St.,

Minoa, N.Y. 13116 [22] Filed: Aug. 1, 1973 [21] Appl. No.: 384,774

Primary ExaminerMeyer Perlin Attorney, Agent, or FirmJ. Raymond Curtin;Barry E., Deutsch [57] ABSTRACT A combination equalizer andover-pressure control for use with fluid compressors comprises a passagehaving a first piston including a relief port therethrough, the pistonwhen in a first position preventing any flow of fluid through a secondrelief port. A second piston, disposed upstream of the first piston, ismovable relative thereto. A first spring provides a force to maintainthe second piston in spaced relationship relative to the first piston,the second piston moving into scaling abutment with the first piston toclose the first relief port when fluid pressure acting on the secondpiston exceeds a predetermined value. A second spring provides a forceto maintain the first and second pistons in position relative to thesecond relief port to prevent any fluid flow therethrough. The first andsecond pistons move jointly at a predetermined over-pressure conditionto open the second relief port. Upon the deenergization of the fluidcompressor the second piston moves relative to the first piston, wherebythe first relief port is opened to relatively quickly equalize pressuresacross the control.

2 Claims, 3 Drawing Figures PATENTED [H5824 I974 sum 1 hr 2 YFIG.I

COMPRESSOR CONTROL FOR REFRIGERATION SYSTEM BACKGROUND OF THE INVENTIONThis invention relates to fluid compressors and more particularly to acombined pressure equalizer and overpressure control for use with fluidcompressors.

Refrigeration units employing fluid compressors typify applications inwhich there exists a substantial pressure differential across thecompressor following shutdown and normally for a number of hoursthereafter. If it is desired to restart the compressor during the periodof time when the pressure differential exists, the compressor motor mustnot only have sufficient torque to overcome the inherent inertia of thecompressor parts, but it must also overcome the pressure differential inorder to restart the compressor. The foregoing necessitates theutilization of either oversized motors or relatively expensive startingaccessories.

In U.S. Pat. No. 3,398,551, assigned to the assignee of the instantinvention, there is disclosed a compressor control which functions torapidly equalize the pressure between the suction and discharge sides ofthe compressor to thereby eliminate the necessity for having startingaccessories or the need for using oversized motors. In addition, thecontrol disclosed in the aforecited patent operates to protect the fluidcompressor during overpressure conditions.

Although the device disclosed in the aforementioned patent has proven tobe extremely satisfactory from a functional standpoint, it has beenfound that certain of the parts of such control wear more rapidly thandesired. In addition, equalization between the discharge and suctionside of the compressor is not accomplished quite as rapidly as desireddue to internal friction produced bythe relative motion of the parts andin particular due to the utilization of an O-ring for sealing purposes.1

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide a compressor control which permits rapid equalization betweenthe dischargeand suction side of the compressor, as well as protects thecompressor during overpressure conditions.

It is a further object of the invention to reduce movement of parts ofthe control to thereby decrease wear thereof.

It is a further object of this invention to eliminate the need forO-rings or similar sealing devices to thereby eliminate internalfriction to increase the rate at which equalization occurs.

These and other objects of the present invention are obtained byproviding a control device having a passage adapted to conduct pressurefluid. A first pistonlike member includes a relief port therethrough,the member when in a first position preventing any flow of fluid througha second relief port. A second piston-like member is disposed upstreamof the first piston-like member for relative movement therebetween.First force supplying means operates to maintain the second member inspaced relationship relative to the first member, the second piston-likemember moving into sealing abutment with the first member to close thefirst relief port when fluid pressure acting on the second memberexceeds a predetermined value. Second force supplying means operates tomaintain the first and second members in position relative to the secondrelief port to prevent any fluid flow therethrough, the first and secondpiston-like members moving jointly at a predetermined overpressurecondition to open the second relief port. The first force supplyingmeans additionally functions to move the second member relative to thefirst member when the fluid compressor becomes inoperable therebyopening the first relief port. The second piston-like member includesabutment means to maintain the passage means of the control device in anopen state when the first relief port is open to relatively quicklyequalize pressures across the control.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic sectional viewshowing the combination pressure equalizer and overpressure control ofthe present invention as used with a fluid compressor;

FIG. 2 is a schematic sectional view of the control of FIG. 1 showingthe control during occurrence of a compressor overpressure condition;and

FIG. 3 is a schematic sectional view showing the control of FIG. 1following shutdown of the compressor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of thedrawings, there is shown a pressure control 10 of the present inventionas used with a fluid compressor 12. As will be more apparenthereinafter, pressure control 10 equalizes pressures across compressor12 following shutdown of the compressor and protects the compressoragainst excessive internal pressures. In referring to the variousFigures of the drawing, like numerals shall refer to like parts.

In the exemplary showing of the drawing, fluid compressor 12 forms partof a closed fluid pressure unit, more particularly a refrigeration unithavingcondenser l4, expansion device 18 and evaporator 20. In this typeof unit, it is understood that the relatively high pressure vaporousrefrigerant dischargedby compressor 12 is condensed in condenser 14, theliquid refrigerant leaving condenser 14 being expanded by device 18 andthereafter flowing through evaporator 20 where the refrigerant isvaporized. Gaseous refrigerant from evaporator 20 returns throughconduit 22 to compressor 12.

On shutdown of compressor 12, a substantial pressure differential existsacross the compressor. Although a part of the pressure differentialacross the compressor is relatively quickly dissipated, the pressuredifferential remains relatively high for a comparatively extensiveperiod of time. Where compressor motor 13 is a single phase motor, astart accessory must be added to enable motor 13 to overcome thepressure loading on compressor 12 if it is desired to restart thecompressor when a relatively high pressure differential exists. Wheremotor 13 is a three phase motor, it is necessary to provide a motorhaving sufficient starting torque to enable the compressor to berestarted when a relatively high pressure differential exists. The costadvantage in eliminating starting accessories and reducing motor sizeare evident, and pressure control 10 which effectively neutralizespressure loading on a compressor in a relatively short time followingshutdown of the compressor eliminates the need for motor startingaccessories and/or oversized motors.

Pressure control has an outer shell forming a generally cylindricalvalve and piston chamber 26. A first end 29 of chamber 26 communicateswith the outlet or discharge side of compressor 12. The other end 34 ofchamber 26 communicates via conduit 32 and 33 with the inlet or suctionside of the compressor. Additionally, conduits and 32 communicate reliefports 28 which are provided in the wall of the valve, with the suctionside of the compressor.

A first piston-like member 45 is slidably arranged in chamber 26. Spring49, disposed between first pistonlike member 45 and a second piston-likemember 60, urges piston 45 toward end wall 35 of chamber 26.

Piston-like member has a stem-like projection 46. Projection 46 isslidably journaled in coaxial bearing opening 48 provided in secondpiston-like member 60. Piston-like members 45 and 60 are beveledrespectively on opposed surfaces 50 and S4 to form a leaktightconnection when the piston-like members are brought into intimatecontact as will be more apparent hereinafter.

Piston-like member 45 includes abutment members 52 projecting fromsurface 61 thereof. Abutment members contact wall 35 as is illustratedin FIG. 3, upon the compressor being rendered inoperable.

A second spring 56 urges second piston-like member 60 towards wall 35 ofchamber 26. Shoulders 57 formed on the inner wall of chamber 26 limitthe movement of second piston-like member 60 towards wall 35. Stop 58 isprovided to maintain spring 56 in its desired location. Preferably,springs 49 and 56 are formed of belleville washers.

With compressor 12 shutdown, and assuming the pressures between thecompressor inlet and outlet to be substantially equal, spring 49 holdsfirst piston-like member 45 against wall 35 of control chamber 26.Inasmuch as member 45 includes abutment members 52, face 61 of member 45is maintained in spaced relation relative to wall 35 to thereby maintaincommunication between inlet 29 and outlet 34 of the control. Thisposition is illustrated in FIG. 3 of the drawings. As is evident fromFIG. 3, relief port 48 is opened to thereby permit flow from the highpressure side of the control to the low pressure side thereof.

When the compressor is started, the difference in pressure between theinlet and outlet thereof rises. At a predetermined pressuredifferential, pressure acting on piston-like member 45 overcomes theforce supplied by spring member 49 to move piston 45 away from wall 35of chamber 26 towards second piston-like member 60. Second piston-likemember 60 is maintained stationary due to the force supplied by secondspring 56. The opposed beveled faces of the piston-like members engage,thereby closing off any flow through opening 48 of second piston-likemember 60. Relief ports 28 are closed by second piston-like member 60.The position of the components of control 10 during normal operation isillustrated in FIG. 1.

With relief port 48 closed, a rise in pressure above the normalcompressor operating pressure is reflected in control 10 and at apredetermined overpressure, the force acting on members 45 and 60overcomes the force supplied by second spring member 56 to move themembers jointly towards stop 58. This directly connects the compressordischarge and suction through relief ports 28. The position of theelements of the control when an overpressure condition exists isillustrated in FIG. 2 of the drawings. Spring 56 urges piston-likemembers 45 and to their normal operating position illustrated in FIG. 1when the over-pressure condition has been eliminated.

When compressor 12 is shut down, the existing pressure differentialacross compressor 12 undergoes an initial decrease as pressures aredissipated due to internal leakage within the various components of therefrigeration unit. Following this initial decrease in pressuredifferential across the compressor, the rate of decrease of the pressuredifferential falls quite substantially. First spring-like member 49urges piston-like member 45 towards wall 35 of chamber 26; however face61 of member 45 is maintained in spaced relation relative to wall 35 bythe projecting abutment members 52. The continued communication betweenthe high pressure and low pressure sides of the compressor, as providedthrough relief port 48 results in a continuing decrease in the pressuredifferential across the compressor.

The present pressure control operates to rapidly equalize the pressuredifferential across a compressor and also safeguards the compressor fromexcessive internal pressures. The control of the present inventionemploys a limited number of parts having limited movement to therebyincrease the operating life of the control. In addition, the presentcontrol eliminates the need for an O-ring or other internal seal, asexemplified by' the prior art of the heretofore cited United Statespatent; the elimination of such O-ring reduces the internal friction ofthe moving parts to thereby further increase the rate at which thepressure differential is equalized.

While a preferred embodiment of the present invention has been describedand illustrated, it will be understood that the invention is not limitedthereto, but may be otherwise embodied with the scope of the followingclaims.

I claim:

1. In a refrigeration unit including a compressor 12) with a first heatexchange coil (14) joined to the discharge side of said compressor,expansion means (18) and a second heat exchange coil (20) joined to thesuction side of said compressor, the improvement comprismg:

a. a combination equalizer and over-pressure control (10) having passagemeans adapted to communicate said compressor discharge side with saidcompressor suction side bypassing said other components of said unit,said passage means including a first piston-like member (60) having afirst relief port therethrough, said member when in a first positionpreventing any flow of fluid through a second relief port (28);

b. means for closing said first relief port including a secondpiston-like member (45), said second piston-like member being disposedupstream of said first piston-like member, said first and second membersbeing movable relative to one another;

c. control means including first means (49) providing a force tomaintain said second member in spaced relationship relative to saidfirst member, said second member moving into sealing abutment with saidfirst member to close said first relief port when fluid pressure actingon said second member exceeds a predetermined value, second means (56)providing a force to maintain said first and second members in positionrelative to said second relief means in an open state when said firstrelief port is opened to relatively quickly equalize pressures betweenthe discharge side and the suction side of said compressor.

2. A combination in accordance with claim 1 wherein said first andsecond force supplying means are spring washers.

1. In a refrigeration unit including a compressor (12) with a first heatexchange coil (14) joined to the discharge side of said compressor,expansion means (18) and a second heat exchange coil (20) joined to thesuction side of said compressor, the improvement comprising: a. acombination equalizer and over-pressure control (10) having passagemeans adapted to communicate said compressor discharge side with saidcompressor suction side bypassing said other components of said unit,said passage means including a first piston-like member (60) having afirst relief port therethrough, said member when in a first positionpreventing any flow of fluid through a second relief port (28); b. meansfor closing said first relief port including a second piston-like member(45), said second piston-like member being disposed upstream of saidfirst piston-like member, said first and second members being movablerelative to one another; c. control means including first means (49)providing a force to maintain said second member in spaced relationshiprelative to said first member, said second member moving into sealingabutment with said first member to close said first relief port whenfluid pressure acting on said second member exceeds a predeterminedvalue, second means (56) providing a force to maintain said first andsecond members in position relative to said second relief port toprevent any fluid flow therethrough, said first and second membersmoving jointly at a predetermined over-pressure condition to open saidsecond relief port; and d. said first force supplying means moving saidsecond member relative to said first member when the compressor becomesinoperable thereby opening said first relief port, said second memberincluding abutment means (52) to maintain said passage means in an openstate when said first relief port is opened to relatively quicklyequalize pressures between the discharge side and the suction side ofsaid compressor.
 2. A combination in accordance with claim 1 whereinsaid first and second force supplying means are spring washers.